<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    let num1 = Number(prompt('请输入第一个数：'))
    let num2 = +prompt('请输入第二个数：')
    let num_add = num1 + num2
    alert(`两者之和为${num_add}`)
    document.write(`两者之和为${num_add}`)
  </script>
</body>

</html>